Sir Alex Ferguson has confirmed Wayne Rooney's lack of fitness was the reason behind his omission from the Manchester United side last weekend.

The nasty gash Rooney suffered in the 3-2 win over Fulham and which threatens to rule the striker out for a month obscured his failure to make the Red Devils starting line-up.

Instead, Ferguson preferred new-boys Robin van Persie and Shinji Kagawa, and with both scoring it seems unlikely Rooney would have forced his way into the team at Southampton on Sunday either.

Now the decision does not have to be made.

However, Ferguson did not do much to undermine rumours of his discontent at the condition Rooney returned to training in as he explained the reasoning behind what admittedly was "not an easy decision" for the United boss.

"Wayne's a bit behind other players in terms of fitness," said Ferguson. "He needs a few games.

"I wanted to play Van Persie at Old Trafford, although I knew he wasn't 100% fit either.

"I'd have rather taken him off with 20 minutes to go. It was only because we lost the second goal that I was forced to leave him on.

"It wasn't an easy choice to leave Wayne out because he is a very good player who can score you goals."

Rooney has confirmed there is no rift between him and Ferguson, leaving him free to get on with the business of getting fit.

And despite the severity of the striker's injury, the United boss insists the four week timescale he outlined on Saturday has not changed.

"He was in yesterday," he said.

"It's nothing serious on the actual gash - it's a bad one but it was treated carefully and very quickly and we don't expect any complications.

"The fact it's a gash and not a ligament, muscle or joint injury means he can do a lot of work in the gym so he should be back in four weeks."

Although there have been suggestions United are seeking deals for Federico Macheda and Bebe to find alternative clubs, Ferguson insists his transfer business is done.

Of more concern was his irritation at the Football Association, who he blames for releasing news of the knee injury that has kept Ashley Young out of the Southampton game, plus England's World Cup qualifiers against Moldova and Ukraine.

"It was nice of the FA to let everyone know Ashley Young is injured," he said.

"There's no point in giving them any information now.

"He's out but it's not serious and he'll be ready in a couple of weeks' time."

Ferguson also confirmed Jonny Evans will be available to partner skipper Nemanja Vidic in central defence following his summer ankle operation.

However, neither Rio Ferdinand nor Phil Jones will be considered even though they have returned to training following groin and back problems.

Some fans still believe United are lacking a physical presence in central midfield.

Overall, though, it seems Ferguson has bought well.

Kagawa has been particularly impressive following his £17million move from German champions Borussia Dortmund.

The 23-year-old has not been fazed by joining a club the size of United and revelled in the space just behind Van Persie against Fulham.

"We looked at Kagawa a lot," said Ferguson.

"In his first season at Dortmund he did very well, which was a surprise because he seemed to come from nowhere.

"Last season there was more authority in his game and his goal-scoring was good from that position.

"He was absolutely magnificent when I went to see him in the German cup final against Bayern Munich.

"His movement and awareness of the space in front of him were fantastic.

"He did everything we were looking for and that's why we moved for him."

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